Studies on protein binding of antibiotics. IV. Effect of the binding of drug to 100,000 X g supernatant fluid of rabbit liver homogenates on urinary excretion.

The extent of the binding of beta-lactam antibiotics to 100,000 X g supernatant fluid of rabbit liver homogenates was investigated. Urinary excretion tended to decrease as the extent of the binding to 100,000 X g supernatant fluid increased. Predicting urinary excretion was achieved using the binding to 100,000 X g supernatant fluid and other physicochemical factors. A good coincidence resulted from multiple regression analysis. [14C]Benzylpenicillin binding proteins in rabbit liver were investigated and revealed that the affinity of cefoperazone was much stronger than that of cefazolin.